Deposition process

ABSTRACT

A method of patterning a substrate includes receiving a substrate having microfabricated structures, including mandrels; executing a deposition process that deposits a first material on the mandrels, the deposition process including cyclically moving the substrate through a set of deposition modules. The substrate is moved through the set of deposition modules so that the first material is deposited at a first thickness at top portions of the mandrels and at a second thickness at bottom portions of mandrels, the first thickness being greater than the second thickness. The method includes executing a spacer deposition process that conformally deposits a second material on the substrate; executing a spacer open etch that removes depositions of the second material from over a top surface of the mandrels; removing the first material and the mandrels from the substrate, leaving sidewall spacers; and transferring a pattern defined by the sidewall spacers into an underlying layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/889,260, filed on Aug. 20, 2019, which application is herebyincorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to a system and method forsemiconductor device fabrication, and, in particular embodiments, tomethods for deposition.

BACKGROUND

Generally, advancements in integrated circuit (IC) technology are drivenby a demand for higher functionality at reduced cost. An IC comprises anetwork of electronic components and interconnect elements (e.g.,transistors, resistors, capacitors, metal lines, contacts, and vias)integrated in a monolithic structure. The demand for higherfunctionality at reduced cost is enabled by increasing the packingdensity of elements of the network through miniaturization. The IC isfabricated layer-by-layer by a sequence of deposition and patterning ofdielectric, metal, and semiconductor layers over a semiconductorsubstrate or wafer. At each successive technology node, the minimumfeature sizes are reduced to reduce cost by roughly doubling thecomponent packing density. Features of a few nanometers may be printedwith innovations in direct patterning (e.g., extreme ultraviolet (EUV)and immersion lithography) and in printing at sub-resolution pitchesusing multiple patterning techniques. Some of these techniques usedense, high aspect ratio nanostructures. Providing the capability offorming nanostructures of accurate dimensions along with preciselycontrolled structural features such as edge profile, uniformly across awide (e.g., 300 mm) wafer is a technological challenge. Successfuldeployment of techniques to overcome some of the hurdles in fabricatingscaled semiconductor devices may need further innovations in processingmethods and equipment.

SUMMARY

In accordance with an embodiment, a method of patterning a substrateincludes receiving a substrate having microfabricated structures,including mandrels; executing a deposition process that deposits a firstmaterial on the mandrels, the deposition process including cyclicallymoving the substrate through a set of deposition modules. The set ofdeposition modules include modules for component process of thedeposition process, where the substrate is moved through the set ofdeposition modules so that the first material is deposited at a firstthickness at top portions of the mandrels and at a second thickness atbottom portions of mandrels, the first thickness being greater than thesecond thickness. The method further includes executing a spacerdeposition process that conformally deposits a second material on thesubstrate; executing a spacer open etch that removes depositions of thesecond material from over a top surface of the mandrels; removing thefirst material and the mandrels from the substrate, leaving sidewallspacers; and transferring a pattern defined by the sidewall spacers intoan underlying layer after removing the first material and the mandrelsfrom the substrate.

In accordance with an embodiment, a method of patterning a substrateincludes receiving a substrate having microfabricated structuresincluding mandrels; executing an atomic layer deposition process thatdeposits a first material on the mandrels. The atomic layer depositionprocess includes cyclically moving the substrate through a set of atomiclayer deposition modules. The set of atomic layer deposition modulesinclude modules for component process of the atomic layer depositionprocess, where the substrate is moved through the set of atomic layerdeposition modules at a speed that results in the first material beingdeposited at a first thickness at top portions of the mandrels and at asecond thickness a bottom portions of mandrels, the first thicknessbeing greater than the second thickness. The method includes executing aspacer deposition process that conformally deposits a second material onthe first material; executing a spacer open etch to remove depositionsof the second material from over top surfaces of the mandrels; andremoving the first material and the mandrels from the substrate, leavingsidewall spacers; and transferring a pattern defined by the sidewallspacers into an underlying layer.

In accordance with an embodiment, a method for forming a device includesplacing a substrate within a processing chamber, the substrate includinga microfabricated structure including sidewalls and a top surface;forming a first reaction zone within the processing chamber by flowing afirst precursor gas and a first isolation zone within the processingchamber by flowing an inert gas through the first isolation zone; andexecuting a cyclic deposition process to deposit a cap layer including afirst material over the sidewalls and the top surface of themicrofabricated structure by cyclically moving the substrate in a cyclicmotion within the processing chamber through the first reaction zone andthe first isolation zone, the depositing including having apredetermined relationship between a thickness of the cap layer alongthe sidewalls of the microfabricated structure with the first precursorgas, the cyclic motion of the substrate, a partial pressure of the firstprecursor gas in the first reaction zone, and a thickness of the caplayer over the top surface of the microfabricated structure, based onthe predetermined relationship, selecting the first precursor gas, atarget rate for the cyclic motion, a target partial pressure for thefirst precursor gas, a target deposition time for a target thickness ofthe cap layer over the top surface of the microfabricated structure, anddepositing the cap layer, for the selected target deposition time, atthe selected target rate for the cyclic motion and the selected targetpartial pressure of the first precursor gas.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a flow diagram of a spacer etch mandrel pull process module,in accordance with an embodiment of the invention;

FIG. 2 is a schematic illustrating a perspective view of a semiconductorprocessing equipment, in accordance with an embodiment of the invention;

FIGS. 3A-3D illustrate cross-sectional views of a semiconductor deviceat various intermediate stages of a hypothetical spacer etch mandrelpull process flow;

FIGS. 4A-4E illustrate cross-sectional views of a semiconductor deviceat various intermediate stages of a spacer etch mandrel pull processflow, in accordance with an embodiment of the invention;

FIG. 5 is a graph illustrating side coverage of a cap layer vs. rotationspeed, in accordance with an embodiment of the invention;

FIG. 6 is a flow diagram of a spacer etch mandrel pull process module,in accordance with an embodiment of the invention.

FIG. 7 is a flow diagram of a sidewall image transfer process module, inaccordance with an embodiment of the invention; and

FIG. 8 is a flow diagram of a depth-dependent deposition process, inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The embodiments in this disclosure describe methods of forming a caplayer over a patterned layer, wherein the thickness, t_(S), of thecapping material deposited along the sidewall of a feature (e.g., aline) in the patterned layer is a function of a vertical distance from areference flat top surface of the patterned feature. The verticaldistance is referred to as depth, d, and the deposition method isreferred to as a depth-dependent deposition, or DDD process. Oneadvantage provided by the DDD process is that the depth-dependence oft_(S) may be used to adjust the slope of the sidewalls of patternedfeatures. (Parameters d and t_(S) are illustrated in FIG. 4B.) Forexample, consider a patterned layer wherein the sidewalls of a line formacute angles with the base. If, subsequently, a cap layer is formedhaving a progressively decreasing thickness from top to bottom along thesidewalls then the sidewall slope of the respective feature of thecombined cap layer and patterned layer would be more vertical relativeto the sidewall of the respective uncapped feature.

The DDD process may be useful for adjusting the sidewall slopes ofpatterned features in some applications where it is desirable for thepatterned layer to have features with vertical sidewalls. The sidewallslope is typically characterized by a sidewall angle, θ, defined as theangle formed by the sidewall and the base of a patterned line.Accordingly, θ=90° for a vertical sidewall, θ<90° for tapered sidewalls,and θ>90° for a reentrant sidewall profile. In the embodiments in thisdisclosure, the cap layer thickness on the sidewalls, t_(S), is adecreasing function of d, or the function t_(S)=t_(S)(d) is decreasingwith increasing d. The cap layer is thickest at the top (d=0 nm), andt_(S)(o) is roughly the same as a target thickness, t_(T), of thecapping material deposited over the reference flat top surface. A DDDprocess may be used to adjust θ upwards. For example, for taperedsidewalls, the top of a line in a patterned layer is narrower than therespective base. Thus, the sidewall may be adjusted towards the verticalby forming a cap over the pattern using a DDD process whereby the caplayer on the sidewall is formed thicker towards the top relative to thebase.

One application where vertical sidewalls of a patterned layer may bepreferred is the spacer-etch mandrel pull (SEMP) process module used ina double (or multiple) patterning process flow, commonly referred to asthe sidewall image transfer (SIT) technique. As known to persons skilledin the art, a process flow used to implement the SIT technique comprisesforming spacers selectively along sidewalls of a patterned layer. Inthis disclosure, the DDD process has been applied to alter the shape ofthe sidewalls prior to forming the sidewall spacers. The terms spacerand sidewall spacer may refer to the same structure in this document.

The DDD process is described in this disclosure in the context of itsapplication in the SEMP process module, where the DDD process is used tohelp provide near-vertical spacers for an SIT process. As known topersons skilled in the art, a double patterning process is a processwhereby features may be patterned at half the pitch corresponding to theresolution limit of the photolithography system. In the SIT technique, asacrificial mandrel layer is patterned at the resolution limit for pitchand sidewall spacers are formed around the mandrel lines. The patternedmasking layer comprising lines at half the pitch of the resolution limitfor the lithography are formed by the sidewall spacers that remain aftera mandrel pull process. Generally, the mandrel pattern comprises longlines. An appropriate self-aligned spacer process may be used to formspacers along each side of the mandrel line. After the sacrificialmandrels are selectively removed, a sub-resolution half-pitch pattern ofspacers remain on the substrate, and may subsequently be used as an etchmask to transfer the sub-resolution pattern to a target layer in thesubstrate below, thereby forming a half-pitch patterned layer comprisingthe target material.

FIG. 1 illustrates a flow diagram for an SEMP process module 10. Asindicated in block 15, the incoming wafer has a patterned mandrel layercomprising, for example, lines patterned over a surface of asemiconductor substrate with a pitch at the resolution limit of thelithography. In this disclosure, the patterned mandrel layer of all theincoming wafers of the example SEMP process modules are assumed to havemandrel lines formed with tapered sidewalls (θ<90°). However, in somecases, the final spacer will tilt in after mandrel removal, possibly dueto film stress or some other integration effect. In such cases, theordinarily vertical mandrel (θ=90°) may require an additionaltop-preferential, cap deposition to form spacers with a reentrantprofile (θ>90°) to compensate for the spacer tilt after mandrel removal.

A cap layer is formed over the patterned mandrel layer using a DDDprocess shown schematically in the dashed box 17 in the flow diagramillustrated in FIG. 1. The DDD process shown in box 17 is a cyclic orperiodic deposition loop where the cap layer is formed by multiplepasses through a short deposition cycle illustrated by box 20 in FIG. 1.A target thickness, t_(T), of the capping material may be deposited overa reference flat top surface (as mentioned above) by performing aplurality of cycles, as indicated by the loop shown schematically in box17. The depth dependence of the sidewall cap thickness, t_(S)(d), may beobtained by creating a vertical concentration gradient of reactantsalong the sidewalls by adjusting appropriate processing parameters. Forexample, in each cycle, the exposure time of the wafer to the precursorgases may be controlled to be limited to a short duration for whichthere is insufficient time for the precursor gas to diffuse all the waydown the sidewall to the floor and establish a uniform density ofchemicals in the space between adjacent lines.

As shown in the flow diagram of the SEMP process module 10 illustratedin FIG. 1, each pass through box 20 (or, one cycle of the DDD processloop in box 17) may be, for example, similar to one reaction cycle of anatomic layer deposition (ALD) process comprising a first reaction usinga first precursor gas (block 22), a first purge or isolation with aninert gas curtain (block 24), a second reaction using a second precursorgas (block 26), and a second purge or isolation with another inert gascurtain (block 28), performed successively. As known to a person skilledin the art, in one reaction cycle of an ALD process, two separateself-limiting surface reactions (separated by an inert purge or an inertisolation zone) are performed to deposit one atomic layer of the desiredmaterial covering the entire exposed surface over which the surfacereactions can occur. Some ALD processes may use the single self-limitingsurface reaction of the precursor component of the ALD cycle, such assilicon precursor, followed by a reactant component, such as oxygen,that is not necessarily self-limiting). In a conventional ALD process,an excess of reactants and time is provided for the reactant gases todiffuse to the entire area of the exposed surface and react with thesurface atoms. Accordingly, in one reaction cycle, it may be said thatone complete monolayer of the deposited material is formed over thesurface. However, the amount of capping material deposited during onecycle (box 20) of the DDD process may be insufficient for forming onemonolayer over the entire sidewall, starting from the reference flat topsurface of the mandrel layer all the way to the floor at the base of themandrel line. The total amount of material deposited in one reactioncycle of the DDD process may be less than the respective amount ofdeposited material for a complete monolayer to be formed over thesurface, such as in a conventional ALD process. Accordingly, it may besaid that a fraction of a complete monolayer is formed over the surface.

As described above, the DDD process parameters may be designed to createa vertical precursor concentration profile that decreases withincreasing depth from the reference flat top surface of the mandrellayer. The higher density of reactants towards the top may result in amore complete surface coverage over an upper portion of the sidewallsrelative to a lower portion of the respective sidewalls in each cycle(box 20) of the cap layer DDD process loop (box 17). Thus, during eachpass, more material is deposited on the upper portion of the sidewallsthan the lower portion of the sidewalls. Accordingly, with multiplepasses through the cap layer deposition cycle (box 20), the cappingmaterial gets preferentially deposited on the upper portion of thesidewalls. The DDD process is complete when the target thickness, t_(T),of the cap is achieved over the reference flat top surface of themandrel layer. The respective sidewall thickness profile of the caplayer, t_(S)(d), decreases with d, starting from a maximum topthickness, t_(S)(0)≈t_(T), as desired.

One purpose of using the DDD process loop (box 17) to form the cap layerin the example flow for the SEMP process module 10 is to adjust thetapered sidewalls of the incoming mandrels to the more vertical edgeprofile of the capped mandrels by applying the sidewall angle adjustmentfeature of the DDD process, as mentioned above. The near-verticalsidewalls of the capped mandrels get mirrored onto near-vertical edgesof the respective sidewall spacers formed over the capped mandrels. Asmentioned above, the patterned layer comprising these spacers isintended for use as the sub-resolution half-pitch etch mask in an SITdouble-patterning process. Vertical edges are preferred for features ina patterned masking layer in order to improve the fidelity of the imagetransfer during the masked etch. Accordingly, incorporating the DDDprocess in the SEMP process module 10 provides an advantage forhigh-fidelity image transfer in the respective SIT double-patterningprocess. In some embodiments, the cap layer deposition method, forexample, the ALD method may cause an erosion of the mandrel shape,causing the sidewall angle of the mandrel to change from verticality, inwhich case the DDD cap deposition may be used to compensate for thatdeposition erosion.

Embodiments of the DDD process may be implemented using, for example, acommercially available spatial atomic layer deposition (ALD) depositionsystem, as described in further detail below with reference to FIG. 2.As explained in further detail below, the spatial ALD system allows aconvenient way to control the exposure time of a wafer to a gaseousreactant by controlling the speed with which the wafer is moved throughan isolated zone containing the respective gaseous mixture comprisingthe precursor gas.

Still referring to FIG. 1, sidewall spacers may be formed over thecapped mandrels after the DDD process loop (box 17) is complete. Thesurface of the floor between adjacent capped mandrels may havenegligible amount of capping material formed if a selective depositionprocess is used to form the cap selectively over the mandrel. Evenotherwise, because of the depth dependence of the deposition rate in theDDD process, the floor would have very little capping material.Generally, a surface clean step may be unnecessary after the DDD step iscompleted.

In block 40, a spacer layer is formed conformally over the wafersurface. The spacer layer comprises a material that may be etchedselectively with an etch chemistry that is chosen for the etch to stopon the adjacent layers, such as the cap layer and the floor betweenadjacent mandrels. However, because the cap layer is a sacrificiallayer, in some embodiments, removal rate of the spacer material duringthe spacer open etch (described below in reference to block 50) may notbe much higher than the removal rate of the capping material. Inaddition, the spacer material is selected to have a sufficiently lowremoval rate when exposed to the etchants used in subsequent etchingprocesses that remove the sacrificial capped mandrels. In someembodiments, the spacer deposition described by block 40 could be acontinuation of the DDD process using a slower rotation rate for trueALD coverage, and a different material for integration purposes.

In block 50, a spacer open etch is performed using an anisotropicetching technique (e.g., reactive ion etching (RIE)). In a spacer openetch, the spacer material may be removed selectively from thesubstantially horizontal surfaces comprising the surface of the floorand the top surface of the capped mandrels, thereby forming sidewallspacers adhering to the near-vertical edges of the capped mandrels. Insome embodiments, the spacer open etch may remove the capping materialfrom the top surface and expose the top surface of the incoming mandrellayer, which would etch through any residual capping material at thesubstrate surface.

The SEMP process module 10 is completed in block 60 of the flow diagramillustrated in FIG. 1. In block 60, the sacrificial patterned cappedmandrel layer is removed selectively, leaving behind the sub-resolutionhalf-pitch pattern of spacers with near-vertical edges. One or more etchsteps may be used to remove the capped mandrel layer. For example, inone embodiment, the capping material may be different from the materialused for the tapered mandrel layer of the incoming wafer in block 15,and two etch steps using two different etchants may be used to removethe capped mandrel layer. A first etch step may remove the cap layer anda second etch step may remove the tapered mandrel layer below the caplayer. In another embodiment, the capping material may be the same asthe mandrel material, and a single etchant may be used to remove thecapped mandrel in a single etch step. The etchants used in block 6 o maybe selected to have a very low removal rate for the spacer material andthe material for the floor between the mandrels so that the cappedmandrels may be removed selectively. In many applications, the patternedspacer layer is used as a mask for patterning a critical dimension wherehigh pattern quality is desired. Insufficient selectivity to the spacermaterial during removal of the capped mandrel layer may cause etchdamage to the sub-resolution half-pitch patterned spacer layer, forexample, increased line edge roughness and increased variability inspacer width. Insufficient selectivity to the floor material duringremoval of the capped mandrel layer may result in severe undercutting ofthe floor material below the spacers, resulting in defects such asdeformed or toppled spacers.

FIG. 2 illustrates a perspective view of a spatial ALD system 100 thatmay be used to perform the DDD process. As mentioned above, one methodby which a higher deposition rate may be achieved closer to the top ofthe mandrel lines is by reducing the time available for a precursor gasto diffuse down towards the floor in one reaction step of the ALDreaction cycle. The DDD process may be implemented in the spatial ALDsystem 100 using this method.

As known to a person skilled in the art, ALD systems may be broadlycategorized as either temporal or spatial. In temporal ALD, the reactioncycle is performed with the wafer stationary in one processing chamber.The first reaction and the second reaction of one ALD reaction cycle ofa temporal ALD system are performed by introducing the respectiveprecursor gas during temporally separated pulses, but at the samespatial location. Each ALD reaction pulse is preceded by an inert purgepulse to clear the chamber of any residual precursors and gaseousreaction byproducts.

In spatial ALD, the wafers are moved through the various gaseousmixtures in spatially separate regions or zones during processingthrough one ALD reaction cycle. Each gaseous mixture is substantiallyconfined to its respective zone; hence, the zones may be described asisolated zones. The wafers are passed through an inert isolation zonebefore entering any one of the two reaction zones. In a spatial ALDsystem, the isolation zone acts as an inert gas curtain at the entrancein front of a reaction zone.

In FIG. 2, six wafers 120 are shown loaded onto a rotating susceptor 130of the spatial ALD system 100. The wafers are moved through a firstgaseous mixture comprising the first precursor gas confined to a firstreaction zone 140, and through a second gaseous mixture comprising thesecond precursor gas confined to a second reaction zone 160.

Two inert isolation zones 150 and 180 are inserted between the tworeaction zones 140 and 160, on either side of the reaction zones. Thereaction zones 140 and 160 are thereby separated in space by inertisolation zones 150 and 180 instead of being separated in time by inertpurge pulses for temporal ALD, as mentioned above. A gas flow systemthat may introduce the various gaseous mixtures in their respectivezones, and a vacuum system that may remove gaseous reaction byproductsthrough two exhausts 110 in the reaction zones 140 and 160 are used tomaintain the composition and pressure of the gases in the various zones.Independently controlled pumps may be used to allow the gaseous mixturein the first reaction zone 140 to be adjusted independent of the gaseousmixture in the second reaction zone 160.

In one embodiment, one ALD reaction cycle may be executed on a wafer 120during one revolution of the susceptor 130. In FIG. 2, an arrow shapedas a half-circular arc indicates the direction of rotation of thesusceptor. Each wafer 120 moves successively through six spatiallyisolated zones 140, 150, 160, 170, and 180 indicated by six dashed arcswith two arrowheads. Accordingly, in one revolution of the susceptor130, a wafer 120 goes through the first reaction zone 140 marked asprecursor absorption, followed by a nitrogen isolation zone 150 whereany residual first precursor gas and gaseous reaction byproduct adheringto the wafer 120 is cleared away. The wafer 120 then enters the secondreaction zone 160 where, in this example embodiment, an oxidationreaction is performed. After passing through the second reaction zone160 the wafer 120 is moved through a plasma treatment zone 170. In someembodiments, the plasma treatment may be used for cleaning the surfacebefore the ALD process is initiated. The plasma treatment may also beused for curing the deposited material. In some other embodiments, theplasma treatment may be optional. The wafer 120 then goes throughanother nitrogen isolation zone 180 to clear the surface of any residualsecond precursor gas and gaseous reaction byproduct before proceedingagain to the first reaction zone 140. The ALD reaction cycle is repeatedin this manner multiple times. The number of repetitions may becontrolled in accordance to a target thickness for the reference flattop surface specified in the respective process recipe. Generally, thethickness of the cap layer on the reference flat top surface is roughlyproportional to a product of the processing time and the rotationalspeed of the susceptor 130.

In one embodiment, the DDD process is implemented by selecting theduration for which the wafer 120 is exposed to the first precursor inone reaction cycle. In the spatial ALD system 100 described above, theduration for which the wafer 120 is exposed to the first precursor inone reaction cycle is the time taken by a wafer 120 to pass through thefirst reaction zone 140. The time taken by a wafer 120 to pass throughthe first reaction zone 140 is roughly inversely proportional to therotational speed of the susceptor 130. Accordingly, the DDD process maybe implemented by adjusting the rotational speed of the susceptor to anappropriate value.

Although a rotational movement is shown in FIG. 2, in alternativeembodiments, a periodic oscillation (e.g., bidirectional motion) of thewafer may produce a similar effect. In such an embodiment, the wafercould be translated from one spatially isolated zone to another duringone half cycle while repeating the same in the opposite direction duringthe other half cycle.

A hypothetical SEMP process module having ideal vertical mandrel edgeprofiles is illustrated by the cross-sectional views in FIGS. 3A-3D. Thehypothetical SEMP process module may be compared with an exampleembodiment of the SEMP process module 10 incorporating the sidewallangle adjustment technique, described above with reference to FIGS. 1and 2. The example embodiment of the SEMP process module 10 is describedwith reference to FIGS. 4A-4E.

FIG. 3A shows a hypothetical ideal incoming wafer and FIG. 4Aillustrates a respective incoming wafer of an example embodiment of theSEMP process module 10. In FIG. 3A, the incoming wafer has a patternedmandrel layer 210 comprising mandrel lines with ideally verticalsidewalls formed over a semiconductor substrate 200. In contrast, therespective incoming wafer in FIG. 4A illustrates a tapered mandrel layer250 comprising patterned mandrel lines with tapered sidewalls.

In FIG. 3B, a conformal spacer layer 220 is formed over the mandrellayer 210 and, in FIG. 3C, an anisotropic spacer open etch is performedto remove the spacer material from the horizontal surfaces, therebyforming sidewall spacers 230. The sidewalls of the conformal spacerlayer 220 (in FIG. 3B) and the sidewall spacers 230 (in FIG. 3C) arealso vertical since they follow the vertical edges of the mandrel layer210. The patterned mandrel layer 210 is selectively removed in FIG. 3D,leaving behind a desired pattern of vertical spacers with spaces 240 inthe places where the mandrels were present.

If the same process steps, described with reference to FIGS. 3B and 3C,were to be performed using the tapered mandrel layer 250, the edges ofthe respective spacers would conform to the tilt of the lines of thetapered mandrel layer 250. Accordingly, once the mandrels of the taperedmandrel layer 250 are removed, each pair of the remaining spacers thatwere formed on opposing sides of a line of the of the tapered mandrellayer 250 would be tilted towards each other in an inward direction intothe space between them where the tapered mandrel layer 250 was presentprior to its removal. As explained above, embodiments of the SEMPprocess module 10 provide the advantage of forming spacer etch maskswith spacers having near-vertical edges despite starting with apatterned layer comprising a pattern of mandrel lines having undesirabletapered sidewalls. An example embodiment is described below withreference to FIGS. 4A-4E.

FIG. 4A illustrates a cross-sectional view of a semiconductor substrate200 after coating a photoresist and patterning the photoresist to formphotoresist lines of the tapered mandrel layer 250 having taperedsidewalls. In other embodiments, the material used for the sacrificialtapered mandrel layer 250 may comprise some other material such assilicon, silicon oxide, silicon nitride, titanium oxide, titaniumnitride, or the like. In one embodiment, the surface of thesemiconductor substrate may comprise silicon oxide formed, for example,by oxidizing the surface of a crystalline silicon wafer. In some otherembodiments, the surface of the semiconductor substrate may be someother material such as silicon nitride, silicon carbide, compoundsemiconductor materials such as GaN, InP, InSb, GaAs, or a metal oxide.

The sidewall angle, θ, of the lines of the tapered mandrel layer 250 maybe about 80°, in this example, and may be from about 70° to about 87° invarious other embodiments. In one embodiment, the lines of the taperedmandrel layer 250 may be patterned at a dense pitch corresponding to theresolution limit of the photolithography system. In this exampleembodiment, the pitch of the mandrel layers 250 may be about 36 nm andthe height of the photoresist mandrel of the tapered mandrel layer 250may be about 95 nm. In various embodiments, the pitch may be from about20 nm to about 100 nm, and the height may be from about 65 nm to about 1m.

FIG. 4B illustrates a capped mandrel layer comprising a cap layer 260formed over the tapered mandrel layer 250 using the DDD process. Aftercompleting the DDD cycles, a surface clean step may be performed toremove any capping material from over a portion of the surface of thesemiconductor substrate 200 that is the floor of the region betweenadjacent mandrels, as described above with reference to FIGS. 1 and 2.In the example embodiment illustrated in FIG. 4B, the thickness of thecap layer 260 over the reference flat top surface of the line of thetapered mandrel layer 250 may be about 15 nm and may comprise titaniumoxide. In various other embodiments, the respective thickness of the caplayer 260 may be from about 5 nm to about 30 nm, and may comprisesilicon, silicon oxide, silicon nitride, titanium nitride, or the like.In some embodiments, the cap layer 260 may comprise the same materialthat has been used to form the tapered mandrel layer 250.

The DDD process used to deposit the titanium oxide of the cap layer 260in this example embodiment has been implemented using the spatial ALDsystem 100, as described above with reference to FIG. 2. In thisexample, the adjustable processing parameters that may be used to adjustthe depth-dependence of the deposition rate are the rotational speed ofthe rotating susceptor 130 and the composition of the first gaseousmixture comprising the first precursor gas in the first reaction zone140 (see FIG. 2). In one embodiment, the rotational speed may be set at60 rpm and the first precursor gas with no extra dilution of the firstgaseous mixture used in the first reaction zone 140 (see FIG. 2). Invarious embodiments, the rotational speed may be set between 1 rpm and240 rpm, and between 30 rpm and 500 rpm in one embodiment.

In one embodiment, using the spatial ALD system 100, the gaseous mixturein the first reaction zone 140 comprises the first precursor gasTetrakis (DiMethylAmino) Titanium (TDMAT) mixed with argon as thecarrier gas at flow rate of about 60 sccm and associated TDMAT transferwith a TDMAT ampoule temperature at about 40° C. The gaseous mixture inthe second reaction zone comprises ozone at flow rates of about 6000sccm at 300 g/m³ density. Other embodiments may use TriMethylAluminum(TMA) as the first precursor gas and oxygen plasma, as the secondprecursor gas. In one embodiment, the reaction temperature may be set toa low value of about 100° C. and 350° C. by controlling the temperatureof the susceptor 130 on which the wafers 120 are loaded (see FIG. 2). Inone embodiment, nitrogen is used to create the inert curtain in theisolation zones 150 and 180, as indicated in FIG. 2. The flow rate ofnitrogen gas may be from about 1 sccm to about 4000 secm. The pressurewas maintained at about 1.6 Torr to about 2 Torr, for example, about 1.5Torr.

In various embodiments of the SEMP process module 10, the flow rate ofthe first precursor carrier gas may be from about 10 sccm to about 1000secm. Also, in various embodiments, the flow rate of the secondprecursor (reactant) gas may be from about 6000 sccm to about 20000sccm, and the flow rate of the respective nitrogen or argon carrier gasmay be from about 1 sccm to about 20000 sccm. In various embodiments,the temperature may be controlled from room temperature to about 400°C., and the pressure may be controlled from about 1 Torr to about 2Torr.

In one embodiment of the SEMP process module 10, the rotational speed ofthe rotating susceptor and the composition of the first gaseous mixturecomprising the first precursor gas in the first reaction zone 140 wereadjusted for the DDD process to adjust the depth-dependence of thedeposition rate. In addition to these processing parameters, the totalchange in the sidewall angle, Δθ, would increase if the targetthickness, t_(T), is increased. An increase in the sidewall angle, Δθ,of about 5° to about 10° may be provided (depending on the height of themandrel and the thickness of the deposited film) using the parametersdescribed above for the example embodiment of the SEMP process module 10in order to provide near-vertical edges of the capped mandrelscomprising the cap layer 260 and the tapered mandrel layer 250, asillustrated in FIG. 4B.

A spacer layer 220 may be formed conformally over the capped mandrellayer comprising the cap layer 260 and the tapered mandrel layer 250, asillustrated in FIG. 4C. In one embodiment, the spacer layer 220 maycomprise silicon nitride having a thickness of about 4 nm to about 10nm. Any suitable deposition technique may be used such as chemical vapordeposition (CVD), plasma-enhanced CVD (PECVD), or ALD, or the like. Invarious embodiments, the spacer layer 220 may comprise silicon oxide,silicon nitride, silicon oxynitride, silicon carbide, or metal oxides,or the like having a thickness from about 5 nm to about 30 nm, or moredepending on the target pattern dimension. The materials selected forthe surface of the semiconductor substrate 200, the tapered mandrellayer 250, the cap layer 260, and the spacer layer 220 may be such thatthe various etch processes used in the SEMP process module 10 are ableto provide the etch selectivity required for the respective etch step.

In FIG. 4D, the sidewall spacers 230 are formed by an anisotropic etchprocess using, for example, an RIE technique that selectively removesthe silicon nitride from over the horizontal surfaces. As illustrated inFIG. 4D, the anisotropic etch process may expose the top surfaces of thecap layer 260 and the semiconductor substrate 200 while silicon nitrideremains along the sidewalls of the capped mandrels comprising the caplayer 260 and the tapered mandrel layer 250. In some other embodiments,the anisotropic spacer open etch may remove the capping material fromover the horizontal surfaces and expose the top surfaces of the taperedmandrel layer 250. The near-vertical edges of the capped mandrels arereflected in the near-vertical edges of the sidewall spacers 230.

The mandrel pull in the example embodiment of the SEMP process module 10is illustrated in FIG. 4E. The titanium oxide cap layer 260 may beremoved by a plasma etch process that has suitable etch selectivityagainst sidewall spacers 230 and the semiconductor substrate 200, e.g.,including an oxide layer, for example, by exposing the wafer to achlorine plasma or chlorine-based plasma. Removal of the cap layer 260may be followed by selective removal of the photoresist tapered mandrellayer 250 using any suitable etch process, for example, exposing thewafer to an oxygen plasma. In FIG. 4E, the spaces 240 vacated byremoving the capped mandrels are shown flanked on each side by thesidewall spacers 230. The spacer pattern comprising the near-verticalsidewall spacers 230 in FIG. 4E is similar to the respective spacerpattern in the hypothetical flow described above with reference to FIG.3D.

The results of an experiment, wherein various sidewall thicknessprofiles, t_(S)(d) are obtained by varying the susceptor rotation speedand the first precursor concentration, are described with reference toFIG. 5. Various titanium oxide cap layers over tapered photoresist lineshave been formed using the spatial ALD system 100, similar to the caplayer 260 over the tapered mandrel layer 250 in the above exampleembodiment. The two processing parameters that modulate thedepth-dependence deposition rate of the respective DDD process, thesusceptor rotation speed and the composition of the first gaseousmixture comprising the first precursor gas, have been varied to obtaintitanium oxide cap layers with various sidewall thickness profiles,t_(S)(d). The target thickness t_(T) over the top surface of the lineshas been kept fixed at t_(T)=3 nm to 12 nm.

FIG. 5 illustrates a plot of a ratio (t_(S)/t_(T)) vs. susceptorrotation speed for two different compositions of the first gaseousmixture comprising the first precursor gas. In FIG. 5, t_(S) has beenmeasured at a fixed depth. Two curves of (t_(S)/t_(T)) vs. rotationspeed are shown corresponding to the two different concentrations of thefirst precursor gas. For the curve labeled “undiluted precursor” thecomposition of the first gaseous mixture roughly matches the respectivecomposition used in the example embodiment of the SEMP process module10, described with reference to FIGS. 4A-4E. In the other curve, theconcentration of the first precursor has been diluted by increasing theflow rate of nitrogen from 2 slm to 4 slm.

In both curves in FIG. 5, (t_(S)/t_(T)) at the fixed depth may bereduced from 100% at the top (d=0 nm) to between 20% and 30% at thefixed depth by increasing the rotation speed beyond a threshold speed.Diluting the first precursor gas reduces the downward flux of theprecursor chemical; hence, the threshold rotation speed is shifted down.As the rotation speed is increased beyond the threshold rotation speed,the ratio (t_(S)/t_(T)) reduces progressively to about 30% for theundiluted first precursor gas and to about 20% for the diluted firstprecursor gas.

Process characterization data such as the data displayed in the curvesplotted in FIG. 5 may be collected from a plurality of experimentalwafers. The characterization data may be analyzed to extract arelationship between t_(S)(d) and selected parameters of the DDD processsuch as rotational speed of the susceptor, precursor concentration inthe gaseous mixture, and the target thickness. The relationship may berecorded graphically or as a numerical model in tabular, mathematical,or some other form and used subsequently to configure a spatial ALDsystem to perform a DDD process to help achieve a targeted sidewallthickness profile, t_(S)(d), and sidewall angle Θ.

Example embodiments of a deposition method have been described forforming a cap layer having a controlled nonuniform, depth-dependentthickness of the capping material formed along the sloped sidewalls ofpatterned features. The vertically nonuniform thickness profile,t_(S)(d), (where d is the depth from the top surface of the feature) isachieved with a controlled vertically nonuniform deposition rate of theDDD process, wherein the deposition rate at a depth, d, reduces withincreasing d. The vertical nonuniformity of the deposition rate reflectsthe nonuniformity of a vertically decreasing concentration profile ofthe precursor gases along the sidewalls.

The method by which the DDD process achieves such a concentrationprofile is using a cyclic deposition loop where, in one cycle, theprecursor species diffuse a limited distance downwards from the toptowards the floor of patterned features. The DDD processes describedabove are performed on incoming patterned wafers loaded onto a rotatingsusceptor in a spatial ALD tool. One revolution of the susceptor is onecycle of the DDD process loop during which the susceptor moves thewafers rapidly through two reaction zones containing gaseous mixtures ofreactant and carrier gases and are isolated on either side by inert gasisolation curtains. An average diffusion distance of the precursorsdownwards along the sidewalls depends on the diffusion time and anaverage diffusion velocity, both of which may be controlled by selectingappropriate independent processing parameters. In the embodimentsdescribed above, the diffusion time in one cycle has been controlled bycontrolling the rotational speed of the susceptor, and the diffusionvelocity has been modulated by adjusting the concentration of theprecursor gas in the gaseous mixture in the first reaction zone. Thesetwo parameters may be controlled to adjust the ratio of the capthickness on the sidewall at a depth, d, to that close to the topsurface, (t_(S)(d)/t_(S)(0)). The difference between these twothicknesses, given by Δt_(S)(d)=(t_(S)(d)−t_(S)(0)) is roughlyproportional to the target thickness for the top surface t_(T).Accordingly, a desired thickness profile, t_(S)(d), may be obtained bycontrolling four process parameters of the DDD process implemented in aspatial ALD tool: precursor chemistry, rotational speed of thesusceptor, precursor concentration in the gaseous mixture, and thetarget thickness.

In the example embodiment, precursor concentration in a gaseous mixtureis used as the adjustable parameter for the diffusion velocity of therespective precursor. However, it is understood that some otherparameter may be used, for example, the temperature of the gaseousmixture. Also, although a constant rotational speed has been used, it ispossible to alter the rpm at which the susceptor rotates at differenttimes during the DDD loop to further adjust the thickness profile of thecap layer.

In the example flow diagram for the SEMP process module 10 (see FIG. 1),the DDD process loop has been implemented as an ALD loop, wherein onecycle (box 20) of the DDD process loop (box 17) comprises two separateself-limiting surface reactions using two different precursors, same asis done in one reaction cycle of an ALD loop. As explained above, in theexample embodiment, the time duration set for one revolution of thesusceptor does not provide sufficient reaction time for completecoverage of the sidewall surface with one atomic layer of the cappingmaterial in one cycle of the example DDD process. It is therebyunderstood that alternate embodiments of the DDD may be realized,wherein the precursor concentration profile is vertically nonuniform butthe deposition reaction may not comprise a plurality of self-limitingsub-reactions, as is the case in an ALD reaction cycle. For example, onecycle of the DDD loop, as shown in FIG. 1 box 20, may be modifiedreplacing the ALD reaction cycle comprising blocks 22, 24, 26, and 28with one deposition reaction and one inert gas purge or pass through aninert gas curtain.

FIG. 6 illustrates a flow diagram for an alternate SEMP module 11 thathas been modified from the flow diagram for the SEMP process module 10in FIG. 1 by replacing the ALD reaction cycle (box 20 in FIG. 1) withthe alternate cycle mentioned above. As illustrated in FIG. 6 box 620,one cycle of the DDD process used in the SEMP module 11 comprisesperforming one deposition reaction (block 622) and one inert gas purgeor pass through an inert gas curtain (block 24). The gaseous mixture forthe deposition reaction performed in block 622 may be similar to therespective non self-limiting deposition reaction used for a CVD processused to deposit the capping material. The residual reactants and byproducts may be removed from the wafer during the following inert gaspurge or inert gas isolation step performed in block 24, similar to therespective purge or isolation step in the DDD process used in the SEMPprocess module 10 illustrated in FIG. 1.

The DDD process used in the SEMP module 11 may be executed using aspatial ALD tool similar to the spatial ALD system 100, described abovewith reference to FIG. 2. For example, in one embodiment, the spatialALD system 100 may be configured such that the same gaseous mixturecomprising the reactants and carrier gases for the respective CVDprocess is used in both the reaction zones 140 and 160. In thisconfiguration, during one revolution of the susceptor 130, two of thecycles (box 21 in FIG. 6) of the DDD process loop (dashed box 617 inFIG. 6) are executed as each wafer 120 passes through both the reactionzones 140 and 160. In another embodiment, the deposition reaction may beconfined to one of the two reaction zones, for example, the firstreaction zone 140, and a non-reactive or inert gaseous mixture may beused in the other reaction zone. In that configuration, one ALD reactioncycle is executed on a wafer 120 during one revolution of the susceptor130. A vertically nonuniform reactant concentration profile may becreated using the same method as for the example embodiment of the SEMPprocess module 10 described above, for example, by adjusting therotational speed of the susceptor 130 and the reactant concentration inthe gaseous mixtures in the reaction zones used to deposit the cappingmaterial.

FIG. 7 illustrates a flow diagram of an SIT double patterning method 700of patterning a layer of a substrate. As indicated by block 710, themethod starts with receiving a substrate having microfabricatedstructures, including mandrels. The next block 720 is executing adeposition process that deposits a first material on the mandrels, thedeposition process including cyclically moving the substrate through aset of deposition modules, the set of deposition modules includingmodules for component process of the atomic layer deposition process,wherein the substrate is moved through the set of atomic layerdeposition modules so that the first material is deposited at a firstthickness at top portions of the mandrels and at a second thickness atbottom portions of mandrels, the first thickness being greater than thesecond thickness. The deposition process may be, for example, aspreviously described using FIGS. 1-6. In various embodiments, the firstthickness is at least 10% thicker as compared to the second thickness.As described in various embodiments, the difference between the firstthickness and the second thickness is varied by changing the rotationalspeed of the susceptor on which the substrate is held, changing thedilution of the precursor gas, e.g., by changing the flow of nitrogen orargon, e.g., from 1 slm to 10 slm, particularly between 2 slm and 4 slm,changing the target thickness of the deposition process, changing theprecursor chemistry, for example, by changing the first chemicalreaction of the cyclic process.

After completing the cyclic deposition process (block 720), in block730, the method includes executing a spacer deposition process thatconformally deposits a second material on the substrate. For example,this is described using FIG. 4C. Then, in block 740, the method includesexecuting a spacer open etch that removes depositions of the secondmaterial over a top surface of the mandrels. For example, this isdescribed using FIG. 4D. Once the spacers are formed, the subsequentsteps are removing the mandrels from the substrate, leaving sidewallspacers, as indicated by block 750, for example, this is described usingFIG. 4E. Accordingly, the successive execution of blocks 710, 720, 730,740 and 750 may be done using either the SEMP process module 10(illustrated in FIG. 1) or the SEMP module 11 (illustrated in FIG. 6).The patterned layer of spacers (e.g., sidewall spacer 230 in FIG. 4E)may be used as the patterned masking layer in the SIT double patterningmethod 700 in block 760. The processing in block 760 is transferring apattern defined by the sidewall spacers into an underlying layer.

As explained above, embodiments of a DDD process may be usedadvantageously to achieve high fidelity pattern transfer in multiplepatterning, for example, the double patterning method 700.

The embodiments of DDD processes described in this disclosure follow amethod illustrated in the flow diagram in FIG. 8.

The DDD process is initiated by placing a substrate within a processingchamber, the substrate comprising a microfabricated structure comprisingsidewalls and a top surface, as indicated in block 810. The processingchamber is configured by forming a first reaction zone within theprocessing chamber (block 820) by flowing a first gaseous mixturecomprising a first precursor gas, and forming a first isolation zonewithin the processing chamber (also in block 820) by flowing an inertgas through the first isolation zone. The DDD process is then performedin block 830 by executing a cyclic deposition process by depositing acap layer comprising a first material over the sidewalls and the topsurface of the microfabricated structure by moving the substrate withinthe processing chamber cyclically through the first reaction zone andthe first isolation zone, wherein a first thickness of the cap layer atthe top surface is greater than a second thickness of the cap layer atthe sidewalls. Executing the cyclic deposition process may be, forexample, as previously described using FIGS. 1-6. As also furtherillustrated in FIG. 8 in block 831, this cyclic deposition process mayinclude having a predetermined relationship between a thickness of thecap layer along the sidewalls of the microfabricated structure as afunction of the cyclic motion of the substrate, a partial pressure ofthe first precursor gas in the first reaction zone, and a thickness ofthe cap layer over the top surface of the microfabricated structure. Thepredetermined relationship is extracted from process characterizationdata. An example of process characterization data that may be used inextracting this relationship is described using FIG. 5. As illustratedin block 832, based on the predetermined relationship, the method mayselect a target rate for the cyclic motion, a target partial pressurefor the first precursor gas, and a target deposition time for a targetthickness of the cap layer over the top surface of the microfabricatedstructure. Once these parameters are selected to achieve a targetthickness, the cap layer is deposited by performing the cyclicdeposition process for the deposition time, at the selected target ratefor the cyclic motion and the selected target partial pressure of thefirst precursor gas (block 833). Executing the cyclic deposition processmay be, for example, as previously described using FIGS. 1-6.

Example 1

A method of patterning a substrate, the method including: receiving asubstrate having microfabricated structures, including mandrels;executing a deposition process that deposits a first material on themandrels, the deposition process including cyclically moving thesubstrate through a set of deposition modules, the set of depositionmodules including modules for component process of the depositionprocess, where the substrate is moved through the set of depositionmodules so that the first material is deposited at a first thickness attop portions of the mandrels and at a second thickness at bottomportions of mandrels, the first thickness being greater than the secondthickness; executing a spacer deposition process that conformallydeposits a second material on the substrate; executing a spacer openetch that removes depositions of the second material from over a topsurface of the mandrels; removing the first material and the mandrelsfrom the substrate, leaving sidewall spacers; and transferring a patterndefined by the sidewall spacers into an underlying layer after removingthe first material and the mandrels from the substrate.

Example 2

The method of example 1, further including performing a selective etchprocess after executing the spacer open etch, where the selective etchprocess removes the first material and the mandrels from the substratewithout damaging the sidewall spacers.

Example 3

The method of one of examples 1 or 2, where receiving the substrateincludes loading the substrate on a susceptor disposed within aprocessing chamber, and where the substrate is moved by rotating thesusceptor at a rotational speed greater than 30 revolutions per minute.

Example 4

A method of patterning a substrate, the method including: receiving asubstrate having microfabricated structures including mandrels;executing an atomic layer deposition process that deposits a firstmaterial on the mandrels, the atomic layer deposition process includingcyclically moving the substrate through a set of atomic layer depositionmodules, the set of atomic layer deposition modules including modulesfor component process of the atomic layer deposition process, where thesubstrate is moved through the set of atomic layer deposition modules ata speed that results in the first material being deposited at a firstthickness at top portions of the mandrels and at a second thickness abottom portions of mandrels, the first thickness being greater than thesecond thickness; executing a spacer deposition process that conformallydeposits a second material on the first material; executing a spaceropen anisotropic etch to remove depositions of the second material fromover top surfaces of the mandrels; and removing the first material andthe mandrels from the substrate, leaving sidewall spacers; andtransferring a pattern defined by the sidewall spacers into anunderlying layer.

Example 5

The method of example 4, where the first thickness is at least 10%thicker as compared to the second thickness, where the atomic layerdeposition process is performed at a temperature between 100° C. and350° C.

Example 6

The method of one of examples 4 or 5, further including controlling asidewall angle of the sidewall spacers between 89° and 91° bycontrolling the difference between the first thickness and the secondthickness.

Example 7

The method of one of examples 4 to 6, where receiving the substrateincludes loading the substrate on a susceptor to execute the atomiclayer deposition process; and where moving the substrate includesrotating the susceptor at a rotational speed between 30 revolutions perminute and 500 revolutions per minute to control a difference betweenthe first thickness and the second thickness.

Example 8

The method of one of examples 4 to 7, where the set of atomic layerdeposition modules includes a first reaction module, further includingdiluting a first gaseous mixture including a first precursor gas bynitrogen gas or argon gas to control the difference between the firstthickness and the second thickness.

Example 9

A method for forming a device, the method including: placing a substratewithin a processing chamber, the substrate including a microfabricatedstructure including sidewalls and a top surface; forming a firstreaction zone within the processing chamber by flowing a first precursorgas and a first isolation zone within the processing chamber by flowingan inert gas through the first isolation zone; and executing a cyclicdeposition process to deposit a cap layer including a first materialover the sidewalls and the top surface of the microfabricated structureby cyclically moving the substrate in a cyclic motion within theprocessing chamber through the first reaction zone and the firstisolation zone, the depositing including having a predeterminedrelationship between a thickness of the cap layer along the sidewalls ofthe microfabricated structure with the first precursor gas, the cyclicmotion of the substrate, a partial pressure of the first precursor gasin the first reaction zone, and a thickness of the cap layer over thetop surface of the microfabricated structure, based on the predeterminedrelationship, selecting the first precursor gas, a target rate for thecyclic motion, a target partial pressure for the first precursor gas, atarget deposition time for a target thickness of the cap layer over thetop surface of the microfabricated structure, and depositing the caplayer, for the selected target deposition time, at the selected targetrate for the cyclic motion and the selected target partial pressure ofthe first precursor gas.

Example 10

The method of example 9, where the sidewalls include top portionsproximate the top surface and bottom portions separated from the topsurface by the top portions, and where depositing the cap layer includesdepositing, during each pass of the cyclic motion, more of the firstmaterial on the top portions of the sidewalls than the bottom portionsof the sidewalls.

Example 11

The method of one of examples 9 or 10, further including: forming asecond reaction zone within the processing chamber by flowing a secondprecursor gas through the second reaction zone; forming a secondisolation zone within the processing chamber by flowing the inert gasthrough the second isolation zone; and where depositing the cap layerfurther includes converting an intermediate layer formed by the firstprecursor gas in the first reaction zone to the first material in thesecond reaction zone by cyclically moving the substrate in a cyclicmotion within the processing chamber through the second reaction zoneand the second isolation zone.

Example 12

The method of one of examples 9 to 11, where the pressure in the firstreaction zone is between 1.6 Torr and 2 Torr, where the first precursorgas in the first reaction zone is Tetrakis (DiMethylAmino) Titanium(TDMAT), where a source of the TDMAT is maintained at a temperaturebetween 30° C. and 50° C.

Example 13

The method of one of examples 9 to 12, further including: when themicrofabricated structure is within the first reaction zone, depositingthe first material over the sidewalls and the top surface of themicrofabricated structure; when the microfabricated structure is withinthe first isolation zone, purging the first precursor gas from thesidewalls and the top surface of the microfabricated structure; and whenthe microfabricated structure is within the first isolation zoneremoving a byproduct formed during the depositing.

Example 14

The method of one of examples 9 to 13, where one cycle of the cyclicdeposition process is performed with each pass of the cyclic motion ofthe substrate.

Example 15

The method of one of examples 9 to 14, where one cycle of the cyclicdeposition process is performed with each pass of the cyclic motion ofthe substrate.

Example 16

The method of one of examples 9 to 15, where depositing a capping layerincludes, depositing a fraction of a complete monolayer of the cap layerduring each pass of the cyclic motion of the substrate, and where, afterthe deposition of the cap layer, a first thickness of the cap layer atthe top surface is greater than a second thickness of the cap layer atthe sidewalls.

Example 17

The method of one of examples 9 to 16, where placing the substrateincludes loading the substrate on a circular susceptor disposed withinthe processing chamber; and where moving the substrate includes rotatingthe susceptor.

Example 18

The method of one of examples 9 to 17, where the susceptor is rotated ata rotational speed between 1 revolutions per minutes and 240 revolutionsper minute.

Example 19

The method of one of examples 9 to 18, where placing the substrateincludes loading the substrate on an oscillating susceptor disposedwithin the processing chamber; and where moving the substrate includesoscillating the susceptor in a bidirectional motion.

Example 20

The method of one of examples 9 to 19, further including: patterning aphotoresist to form a mandrel including the microfabricated structure;forming spacers on sidewalls of the cap layer; and removing themicrofabricated structure to form a mask.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

What is claimed is:
 1. A method of patterning a substrate, the methodcomprising: receiving a substrate having microfabricated structures,including mandrels; executing a deposition process that deposits a firstmaterial on the mandrels, the deposition process including cyclicallymoving the substrate through a set of deposition modules, the set ofdeposition modules including modules for component process of thedeposition process, wherein the substrate is moved through the set ofdeposition modules so that the first material is deposited at a firstthickness at top portions of the mandrels and at a second thickness atbottom portions of mandrels, the first thickness being greater than thesecond thickness; and executing a spacer deposition process thatconformally deposits a second material on the substrate.
 2. The methodof claim 1, further comprising: executing a spacer open etch thatremoves depositions of the second material from over a top surface ofthe mandrels; removing the first material and the mandrels from thesubstrate, leaving sidewall spacers; and transferring a pattern definedby the sidewall spacers into an underlying layer after removing thefirst material and the mandrels from the substrate.
 3. The method ofclaim 1, further comprising: performing a selective etch process afterexecuting the spacer open etch, wherein the selective etch processremoves the first material and the mandrels from the substrate withoutdamaging the sidewall spacers; and wherein receiving the substratecomprises loading the substrate on a susceptor disposed within aprocessing chamber, and wherein the substrate is moved by rotating thesusceptor at a rotational speed greater than 30 revolutions per minute.4. A method of patterning a substrate, the method comprising: receivinga substrate having microfabricated structures including mandrels;executing an atomic layer deposition process that deposits a firstmaterial on the mandrels, the atomic layer deposition process includingcyclically moving the substrate through a set of atomic layer depositionmodules, the set of atomic layer deposition modules including modulesfor component process of the atomic layer deposition process, whereinthe substrate is moved through the set of atomic layer depositionmodules at a speed that results in the first material being deposited ata first thickness at top portions of the mandrels and at a secondthickness a bottom portions of mandrels, the first thickness beinggreater than the second thickness; executing a spacer deposition processthat conformally deposits a second material on the first material;executing a spacer open anisotropic etch to remove depositions of thesecond material from over top surfaces of the mandrels; and removing thefirst material and the mandrels from the substrate, leaving sidewallspacers; and transferring a pattern defined by the sidewall spacers intoan underlying layer.
 5. The method of claim 4, wherein the firstthickness is at least 10% thicker as compared to the second thickness,wherein the atomic layer deposition process is performed at atemperature between 100° C. and 350° C.
 6. The method of claim 4,further comprising controlling a sidewall angle of the sidewall spacersbetween 89° and 91° by controlling a difference between the firstthickness and the second thickness.
 7. The method of claim 4, whereinreceiving the substrate comprises loading the substrate on a susceptorto execute the atomic layer deposition process; and wherein moving thesubstrate comprises rotating the susceptor at a rotational speed between1 revolutions per minute and 240 revolutions per minute to control adifference between the first thickness and the second thickness.
 8. Themethod of claim 4, wherein the set of atomic layer deposition modulescomprises a first reaction module, further comprising diluting a firstgaseous mixture comprising a first precursor gas by nitrogen gas orargon gas to control the difference between the first thickness and thesecond thickness.
 9. A method for forming a device, the methodcomprising: placing a substrate within a processing chamber, thesubstrate comprising a microfabricated structure comprising sidewallsand a top surface; forming a first reaction zone within the processingchamber by flowing a first precursor gas and a first isolation zonewithin the processing chamber by flowing an inert gas through the firstisolation zone; and executing a cyclic deposition process to deposit acap layer comprising a first material over the sidewalls and the topsurface of the microfabricated structure by cyclically moving thesubstrate in a cyclic motion within the processing chamber through thefirst reaction zone and the first isolation zone, the depositingcomprising having a predetermined relationship between a thickness ofthe cap layer along the sidewalls of the microfabricated structure withthe first precursor gas, the cyclic motion of the substrate, a partialpressure of the first precursor gas in the first reaction zone, and athickness of the cap layer over the top surface of the microfabricatedstructure, based on the predetermined relationship, selecting the firstprecursor gas, a target rate for the cyclic motion, a target partialpressure for the first precursor gas, a target deposition time for atarget thickness of the cap layer over the top surface of themicrofabricated structure, and depositing the cap layer, for theselected target deposition time, at the selected target rate for thecyclic motion and the selected target partial pressure of the firstprecursor gas.
 10. The method of claim 9, wherein the sidewalls comprisetop portions proximate the top surface and bottom portions separatedfrom the top surface by the top portions, and wherein depositing the caplayer comprises depositing, during each pass of the cyclic motion, moreof the first material on the top portions of the sidewalls than thebottom portions of the sidewalls.
 11. The method of claim 9, furthercomprising: forming a second reaction zone within the processing chamberby flowing a second precursor gas through the second reaction zone;forming a second isolation zone within the processing chamber by flowingthe inert gas through the second isolation zone; and wherein depositingthe cap layer further comprises converting an intermediate layer formedby the first precursor gas in the first reaction zone to the firstmaterial in the second reaction zone by cyclically moving the substratein a cyclic motion within the processing chamber through the secondreaction zone and the second isolation zone.
 12. The method of claim 11,wherein the pressure in the first reaction zone is between 1.6 Torr and2 Torr, wherein the first precursor gas in the first reaction zone isTetrakis (DiMethylAmino) Titanium (TDMAT), wherein a source of the TDMATis maintained at a temperature between 30° C. and 50° C.
 13. The methodof claim 9, further comprising: when the microfabricated structure iswithin the first reaction zone, depositing the first material over thesidewalls and the top surface of the microfabricated structure; when themicrofabricated structure is within the first isolation zone, purgingthe first precursor gas from the sidewalls and the top surface of themicrofabricated structure; and when the microfabricated structure iswithin the first isolation zone removing a byproduct formed during thedepositing.
 14. The method of claim 13, wherein one cycle of the cyclicdeposition process is performed with each pass of the cyclic motion ofthe substrate.
 15. The method of claim 9, wherein one cycle of thecyclic deposition process is performed with each pass of the cyclicmotion of the substrate.
 16. The method of claim 9, wherein depositing acapping layer comprises, depositing a fraction of a complete monolayerof the cap layer during each pass of the cyclic motion of the substrate,and wherein, after the deposition of the cap layer, a first thickness ofthe cap layer at the top surface is greater than a second thickness ofthe cap layer at the sidewalls.
 17. The method of claim 9, whereinplacing the substrate comprises loading the substrate on a circularsusceptor disposed within the processing chamber; and wherein moving thesubstrate comprises rotating the susceptor.
 18. The method of claim 17,wherein the susceptor is rotated at a rotational speed between 1revolutions per minutes and 240 revolutions per minute.
 19. The methodof claim 9, wherein placing the substrate comprises loading thesubstrate on an oscillating susceptor disposed within the processingchamber; and wherein moving the substrate comprises oscillating thesusceptor in a bidirectional motion.
 20. The method of claim 9, furthercomprising: patterning a photoresist to form a mandrel comprising themicrofabricated structure; forming spacers on sidewalls of the caplayer; and removing the microfabricated structure to form a mask.